Apparatus and method for measuring erythrocyte sedimentation rate

ABSTRACT

An apparatus and method for measuring an erythrocyte sedimentation rate based on a change in conductivity of blood over time. The apparatus for measuring an erythrocyte sedimentation rate may include: a chamber for holding blood; a pair of electrodes being partially or completely brought into contact with the blood; and a conductivity meter measuring the conductivity through the pair of electrodes. The apparatus and method according to the present invention are less time-consuming than the Westergren method and can acquire a variety of information (for example, hematocrit, dynamics of the sedimentation rate and aggregation of erythrocytes, a relationship between the sedimentation rate and aggregation of erythrocytes, and the like).

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2015-0159141, filed on Nov. 12, 2015, entitled “APPARATUS AND METHODFOR MEASURING ERYTHROCYTE SEDIMENTATION RATE”, which is herebyincorporated by reference in its entirety into this application.

BACKGROUND

1. Technical Field

The present invention relates to an apparatus and method for measuringan erythrocyte sedimentation rate, and, more particularly, to anapparatus and method for measuring an erythrocyte sedimentation ratebased on conductivity of blood measured by a pair of electrodes.

2. Description of the Related Art

Determination of an erythrocyte sedimentation rate (ESR) is a usefulblood test capable of providing an index of inflammation or an acutephase reaction of a patient. The ESR test was invented in 1897 by aPolish physician, Edmund Faustyn Biernacki. Similar methods werereported in 1918 by Robert Sanno Fahraeus and in 1921 by Alf VilhelmWestergren. Particularly, Westergren's method spread quickly all overthe world due to simplicity and low cost thereof.

In the Westergren test, venous blood is mixed with sodium citrate in aratio of 4:1 and then collected in a glass or plastic tube having aminimum sedimentation scale of 200 mm and a minimum bore of 2.55 mm. Thetube is placed on a Westergren stand in a vertical position at roomtemperature for 1 hour. Then, a distance from the lowest point of asurface meniscus to an uppermost layer of an erythrocyte sediment ismeasured. The distance of fall of erythrocytes, expressed as millimetersper hour (mm/h), is recorded as the ESR.

Since the Westergren test takes 1 hour, which is much longer than thetime required for general automated blood tests, a method for measuringan ESR in a shorter period of time is being studied by many researchgroups.

There has been proposed a method of measuring electrical impedance ofblood columns to find an ESR. Resistance of blood is closely relatedwith hematocrit (HCT). A simple equation for finding an ESR using plasmaresistance, membrane capacitance, and HCT may be obtained by linearregression. In addition, time-dependence of the ESR and conductivity hasbeen examined by Cha et al. [1] and Pribush et al. [2-5].

-   [1] Cha K, Brown E F, Wilmore D W. A new bioelectrical impedance    method for measurement of the erythrocyte sedimentation rate.    Physiol Meas. 1994; 15: 499-508.-   [2] Pribush A, Meyerstein D, Meyerstein N. The mechanism of    erythrocyte sedimentation. Part 1: Channeling in sedimenting blood.    Colloid Surf B-Biointerfaces. 2010; 75: 214-223.-   [3] Pribush A, Meyerstein D, Meyerstein N. The mechanism of    erythrocyte sedimentation. Part 2: The global collapse of settling    erythrocyte network. Colloid Surf B-Biointerfaces. 2010; 75:    224-229.-   [4] Pribush A, Meyerstein D, Meyerstein N. The effect of the prior    flow velocity on the structural organization of aggregated    erythrocytes in the quiescent blood. Colloid Surf B-Biointerfaces.    2011; 82: 518-525.-   [5] Pribush A, Hatskelzon L, Meyerstein N. A novel approach for    assessments of erythrocyte sedimentation rate. Int J Lab Hematol.    2011; 33: 251-257.

Such researches focus on the phenomenon that, as erythrocytes settleover time, the HCT decreases at an upper portion of a blood column.

In these methods, electrodes are placed at an upper portion of a bloodcolumn, followed by measuring an ESR based on electrical impedance.However, these methods have a problem in that the erythrocyteaggregation reduces the sensitivity over time, and thus it is impossibleto accurately measure the erythrocyte sedimentation rate.

BRIEF SUMMARY

It is an aspect of the present invention to provide an apparatus andmethod for measuring an erythrocyte sedimentation rate, which is lesstime-consuming than the Westergren method and can acquire a variety ofinformation (for example, hematocrit, dynamics of the sedimentation rateand aggregation of erythrocytes, a relationship between thesedimentation rate and aggregation of erythrocytes, and the like).

In accordance with one aspect of the present invention, there isprovided an apparatus for measuring an erythrocyte sedimentation ratebased on a change in conductivity of blood over time.

The apparatus for measuring an erythrocyte sedimentation rate mayinclude: a chamber for holding blood; a pair of electrodes beingpartially or completely brought into contact with the blood; and aconductivity meter measuring the conductivity through the pair ofelectrodes.

The pair of electrodes may be placed on a bottom surface of the chamber.

The change in conductivity may be found based on a difference betweenconductivities measured at two points of time.

The two points of time may be selected from a time section after theconductivity starts to decrease.

The erythrocyte sedimentation rate may be measured through comparison ofthe change in conductivity with an erythrocyte sedimentation ratemeasured by the Westergren method.

A relationship between the change in conductivity and the erythrocytesedimentation rate measured by the Westergren method may be representedby the following equation:

Δσ=λW ^(γ)

where Δσ denotes a difference (unit: S/m) between blood conductivitiesmeasured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, and λand γ denote fitting parameters, wherein the fitting parameters may becalculated by regression analysis.

The predetermined points of time may be 200 seconds and 400 seconds,respectively, and Δσ may be calculated by σ₂₀₀-σ₄₀₀, wherein σ₂₀₀denotes a conductivity measured when 200 seconds elapse aftererythrocytes start to settle, and σ₄₀₀ denotes a conductivity measuredwhen 400 seconds elapse after erythrocytes start to settle.

The conductivity meter may measure impedance between the pair ofelectrodes to find the conductivity.

A relationship between the change in conductivity and the erythrocytesedimentation rate measured by the Westergren method may be representedby the following equation:

Δσ=λ log(1+W)

where Δσ denotes a difference (unit: S/m) between conductivities of theblood measured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, and λdenotes fitting parameters, wherein the fitting parameters may becalculated by regression analysis.

A relationship between the change in conductivity and the erythrocytesedimentation rate measured by the Westergren method may be representedby the following equation:

${\Delta \; \sigma} = {\lambda \frac{W}{W + \gamma}}$

where Δσ denotes a difference (unit: S/m) between conductivities of theblood measured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, and λand γ denote fitting parameters, wherein the fitting parameters may becalculated by regression analysis.

A relationship between the change in conductivity and the erythrocytesedimentation rate measured by the Westergren method may be representedby the following equation:

${\Delta \; \sigma} = {\lambda \left\lbrack {\left( \frac{1}{\gamma} \right)^{2} - \left( \frac{1}{W + \gamma} \right)^{2}} \right\rbrack}$

where Δσ denotes a difference (unit: S/m) between conductivities of theblood measured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, and λand γ denote fitting parameters, wherein the fitting parameters may becalculated by regression analysis.

In accordance with another aspect of the present invention, there isprovided a method for measuring an erythrocyte sedimentation rate basedon a change in conductivity of blood over time.

The method for measuring an erythrocyte sedimentation rate may include:introducing blood into a chamber; and measuring conductivity of theblood using a pair of electrodes.

The pair of electrodes may be placed in a bottom surface of the chamber.

The change in conductivity may be found based on a difference betweenconductivities measured at two points of time.

The two points of time may be selected from a time section after theconductivity starts to decrease.

The erythrocyte sedimentation rate may be measured through comparison ofthe change in conductivity with an erythrocyte sedimentation ratemeasured by the Westergren method.

A relationship between the change in conductivity and the erythrocytesedimentation rate measured by the Westergren method may be representedby the following equation:

Δσ=λW ^(γ)

where Δσ denotes a difference (unit: S/m) between conductivities of theblood measured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, and λand γ denote fitting parameters, wherein the fitting parameters may becalculated by regression analysis.

A relationship between the change in conductivity and the erythrocytesedimentation rate measured by the Westergren method may be representedby the following equation:

Δσ=λ log(1+W)

where Δσ denotes a difference (unit: S/m) between conductivities of theblood measured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, and λdenotes fitting parameters, wherein the fitting parameters may becalculated by regression analysis.

A relationship between the change in conductivity and the erythrocytesedimentation rate measured by the Westergren method may be representedby the following equation:

${\Delta \; \sigma} = {\lambda \frac{W}{W + \gamma}}$

where Δσ denotes a difference (unit: S/m) between conductivities of theblood measured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, and λand γ denote fitting parameters, wherein the fitting parameters may becalculated by regression analysis.

A relationship between the change in conductivity and the erythrocytesedimentation rate measured by the Westergren method may be representedby the following equation:

${\Delta \; \sigma} = {\lambda \left\lbrack {\left( \frac{1}{\gamma} \right)^{2} - \left( \frac{1}{W + \gamma} \right)^{2}} \right\rbrack}$

where Δσ denotes a difference (unit: S/m) between conductivities of theblood measured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, and λand γ denote fitting parameters, wherein the fitting parameters may becalculated by regression analysis.

According to the present invention, it is possible to provide anapparatus and method for measuring an erythrocyte sedimentation rate,which can measure the erythrocyte sedimentation rate within 400 seconds,which is shorter than the about 1 hour required in the Westergrenmethod, and can easily measure and acquire a variety of information suchas hematocrit, dynamics of the sedimentation rate and aggregation oferythrocytes, a relationship between the sedimentation rate andaggregation of erythrocytes, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will become apparent from the detailed description of thefollowing embodiments in conjunction with the accompanying drawings, inwhich;

FIG. 1 is a view of an apparatus for measuring an erythrocytesedimentation rate according to one embodiment of the present invention;

FIG. 2 is a graph showing conductivities measured on blood sampleshaving different hematocrits (HCTs) after starting of erythrocytesedimentation; and

FIG. 3 is a graph showing correlation between changes in bloodconductivity measured according to one embodiment of the invention andresults of the Westergren ESR test.

DETAILED DESCRIPTION

Hereafter, an apparatus and method for measuring an erythrocytesedimentation rate will be described with reference to the accompanyingdrawings. The above and other aspects, features, and advantages of thepresent invention will become apparent to those skilled in the art fromthe detailed description of the following embodiments in conjunctionwith the accompanying drawings.

As used herein, the term “exemplary” is used to mean serving as an“example, instance, or illustration”. Here, any “exemplary” embodimentor aspect should not be construed as preferred or advantageous overother embodiments or aspects.

As used herein, the terms “comprises,” “comprising,” “includes,” and/or“including,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, components,and/or groups thereof, but do not preclude the presence or addition ofone or more other features, integers, steps, operations, elements,components, and/or groups thereof.

Although the terms first, second, etc. may be used herein to describevarious elements, components, regions, layers, and/or sections, theseelements, components, regions, layers, and/or sections should not belimited by these terms.

As used herein, the singular forms, “a,” “an,” and “the” are intended toinclude the plural forms as well, unless context clearly indicatesotherwise.

FIG. 1 is a view of an apparatus for measuring an erythrocytesedimentation rate according to one embodiment of the present invention.

Referring to FIG. 1, the apparatus for measuring an erythrocytesedimentation rate according to this embodiment of the present inventionmay include: a chamber 101 for holding blood; a pair of electrodes 102a, 102 b for measuring conductivity; a blood injector 103; and aconductivity meter 104.

Blood is introduced into the chamber 101 using the blood injector 103;the pair of electrodes 102 a, 102 b is partially brought into contactwith the blood in the chamber 101; and the conductivity meter 104 maymeasure conductivity between the pair of electrodes 102 a, 102 b.

For example, the conductivity meter 104 may be an impedance analyzerwhich analyzes resistance between the pair of electrodes 102 a, 102 b,thereby finding the conductivity.

According to an exemplary embodiment of the invention, the pair ofelectrodes 102 a, 102 b may be placed on a bottom surface of the chamber101. If the electrodes are placed at an upper portion of the chamber101, it is impossible to accurately measure change in conductivitycaused by sedimentation of erythrocytes toward a bottom of the chamber101 over time.

Once the conductivity is measured by the conductivity meter 104, it ispossible to measure an erythrocyte sedimentation rate through comparisonof the conductivity with an erythrocyte sedimentation rate measured bythe Westergren method.

A relationship between the conductivity and the erythrocytesedimentation rate measured by the Westergren method may be representedby Equations 1 to 4:

Δσ=λW ^(γ)  <Equation 1>

where Δσ denotes a difference (unit: S/m) between conductivities ofblood measured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, λ andγ denote fitting parameters. The fitting parameters are calculated byregression analysis, and λ and γ have values of 0.02049 and 0.254respectively, as calculated by an experimental method according to oneembodiment of the present invention. By way of example, the regressionanalysis may be a least squares method.

Δσ=λ log(1+W)  <Equation 2>

where Δσ denotes a difference (unit: S/m) between conductivities ofblood measured at predetermined points of time; W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method; and λdenotes fitting parameters, wherein the fitting parameters arecalculated by regression analysis, and λ has a value of 0.0145, ascalculated by an experimental method according to one embodiment of thepresent invention. By way of example, the regression analysis may be aleast squares method.

$\begin{matrix}{{\Delta \; \sigma} = {\lambda \frac{W}{W + \gamma}}} & {< {{Equation}\mspace{14mu} 3} >}\end{matrix}$

where Δσ denotes a difference (unit: S/m) between conductivities ofblood measured at predetermined points of time; W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method; and λand γ denote fitting parameters. The fitting parameters are calculatedby regression analysis, and λ and γ have values of 0.085 and 25respectively, as calculated by an experimental method according to oneembodiment of the present invention. By way of example, the regressionanalysis may be a least squares method.

$\begin{matrix}{{\Delta \; \sigma} = {\lambda \left\lbrack {\left( \frac{1}{\gamma} \right)^{2} - \left( \frac{1}{W + \gamma} \right)^{2}} \right\rbrack}} & {< {{Equation}\mspace{14mu} 4} >}\end{matrix}$

where Δσ denotes a difference (unit: S/m) between conductivities ofblood measured at predetermined points of time; W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method; and λand γ denote fitting parameters. The fitting parameters are calculatedby regression analysis, and λ and γ have values of 280 and 60respectively, as calculated by an experimental method according to oneembodiment of the present invention. By way of example, the regressionanalysis may be a least squares method.

Equations 1 to 4 have substantially the same plot in all possible rangesof (0≦W≦200), when λ has a value of 0.0145 and γ has a value of 25.

Preferably, Δσ is calculated by σ₂₀₀-σ₄₀₀. Here, σ₂₀₀ denotes aconductivity measured when 200 seconds elapse after erythrocytes startto settle, and σ₄₀₀ denotes a conductivity measured when 400 secondselapse after erythrocytes start to settle.

FIG. 2 is a graph showing conductivity measured in blood samples havingdifferent hematocrits (HCTs) after starting of erythrocytesedimentation.

Specifically, FIG. 2 shows changes in conductivity over time, asmeasured at an HCT of 35%, 45%, and 55% after starting of erythrocytesedimentation. FIG. 2(A) is a graph obtained by combining graphs plottedfor three HCTs; and FIGS. 2(B), 2(C), and 2(D) are enlarged graphsshowing changes in conductivity measured at respective HCTs before 120seconds elapse.

Referring to FIGS. 2(B), 2(C), and 2(D), it can be seen that theconductivity at each HCT value increases at an early stage whereerythrocytes start to settle. Thereafter, the conductivity at HCTs of35%, 45%, and 55% reaches the maximum values after 18 seconds, 31seconds, and 60 seconds, respectively, and then gradually decreases.

The reason that the conductivity increases at an early stage is becauseaggregation of erythrocytes has a greater influence on conductivity atthe early stage. Aggregation of erythrocytes increases conductivity anderythrocyte sedimentation rate. More specifically, the reason theconductivity increases at an early stage (before 18 seconds elapse whenHCT is 35%, before 31 seconds elapse when HCT is 45%, and before 60seconds elapse when HCT is 55%) is because, at the early stage, theconductivity is more influenced by aggregation of erythrocytes than bysedimentation of erythrocytes which causes reduction in conductivity.

For this reason, according to the present invention, preferably, twopoints of time are selected in a time section where the conductivitystarts to decrease, followed by comparing a difference between theconductivity measured at the two points of time with an erythrocytesedimentation rate found by the Westergren method. More preferably,conductivities at a point of time of 200 seconds and 400 seconds aremeasured such that the erythrocyte sedimentation rate can be measuredwithin 400 seconds while minimizing the influence of erythrocyteaggregation on conductivity.

FIG. 3 is a graph showing correlation between changes in bloodconductivity measured according to one embodiment of the invention andresults of the Westergren ESR test.

As shown in FIG. 3, it can be seen that there is evident correlationbetween changes in blood conductivity measured according to oneembodiment of the invention and results of the Westergren ESR test.

In this embodiment, measurement of changes in blood conductivity and theWestergren ESR test were conducted under the following conditions:

As the chamber 101, a rectangular prismatic polydimethylsiloxane (PDMS)chamber having a width of 4 mm and a depth of 5 mm was used, and, as thepair of electrodes 102 a, 102 b, two gold-plated two-dimensional planarelectrodes each having a width of 300 μm and being placed at a distanceof 1200 μm from one another were used. A portion of each of theelectrodes brought into contact with blood had a length of 4 mm. Theplanar electrodes were fabricated by a typical lithography process.

As the conductivity meter 104, an impedance analyzer (HIOKI IM3570,HIOKI, Corp.) was used. Blood samples were introduced into the chamber101 using a pipette. Each sample was tested three times using the sameequipment. Here, resistance of the blood samples depends on thegeometrical area of the chamber and the electrodes. A KCl standardsolution having a known conductivity value was used to calibrate theequipment. Through calibration, the measured resistance values wereconverted into respective conductivity values.

Although some embodiments have been described with reference to thedrawings, it should be understood that the present invention is notlimited to these embodiments, and that various modifications, changes,and alterations can be made without departing from the spirit and scopeof the invention. Therefore, the scope of the invention should belimited only by the accompanying claims and equivalents thereof.

What is claimed is:
 1. An apparatus for measuring an erythrocytesedimentation rate based on a change in conductivity of blood over time,comprising: a chamber for holding blood; a pair of electrodes partiallyor completely brought into contact with the blood; and a conductivitymeter measuring the conductivity through the pair of electrodes.
 2. Theapparatus according to claim 1, wherein the pair of electrodes is placedon a bottom surface of the chamber.
 3. The apparatus according to claim1, wherein the change in conductivity is found based on a differencebetween conductivities measured at two points of time.
 4. The apparatusaccording to claim 3, wherein the two points of time are selected from atime section after the conductivity starts to decrease.
 5. The apparatusaccording to claim 4, wherein the erythrocyte sedimentation rate ismeasured through comparison of the change in conductivity with anerythrocyte sedimentation rate measured by the Westergren method.
 6. Theapparatus according to claim 5, wherein a relationship between thechange in conductivity and the erythrocyte sedimentation rate measuredby the Westergren method is represented by the following equation:Δσ=λW ^(γ) where Δσ denotes a difference (unit: S/m) betweenconductivities of the blood measured at predetermined points of time, Wdenotes an erythrocyte sedimentation rate (unit: mm/h) measured by theWestergren method, and λ and γ denote fitting parameters, wherein thefitting parameters are calculated by regression analysis.
 7. Theapparatus according to claim 6, wherein the predetermined points of timeare 200 seconds and 400 seconds, respectively, and Δσ is calculated byσ₂₀₀-σ₄₀₀, wherein σ₂₀₀ denotes a conductivity measured when 200 secondselapse after erythrocytes start to settle, and σ₄₀₀ denotes aconductivity measured when 400 seconds elapse after erythrocytes startto settle.
 8. The apparatus according to claim 1, wherein theconductivity meter measures impedance between the pair of electrodes tofind the conductivity.
 9. The apparatus according to claim 5, wherein arelationship between the change in conductivity and the erythrocytesedimentation rate measured by the Westergren method is represented bythe following equation:Δσ=λ log(1+W) where Δσ denotes a difference (unit: S/m) betweenconductivities of the blood measured at predetermined points of time, Wdenotes an erythrocyte sedimentation rate (unit: mm/h) measured by theWestergren method, and λ denotes fitting parameters, wherein the fittingparameters are calculated by regression analysis.
 10. The apparatusaccording to claim 5, wherein a relationship between the change inconductivity and the erythrocyte sedimentation rate measured by theWestergren method is represented by the following equation:${\Delta \; \sigma} = {\lambda \frac{W}{W + \gamma}}$ where Δσdenotes a difference (unit: S/m) between conductivities of the bloodmeasured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, and λand γ denote fitting parameters, wherein the fitting parameters arecalculated by regression analysis.
 11. The apparatus according to claim5, wherein a relationship between the change in conductivity and theerythrocyte sedimentation rate measured by the Westergren method isrepresented by the following equation:${\Delta \; \sigma} = {\lambda \left\lbrack {\left( \frac{1}{\gamma} \right)^{2} - \left( \frac{1}{W + \gamma} \right)^{2}} \right\rbrack}$where Δσ denotes a difference (unit: S/m) between conductivities of theblood measured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, and λand γ denote fitting parameters, wherein the fitting parameters arecalculated by regression analysis.
 12. A method for measuring anerythrocyte sedimentation rate based on a change in conductivity ofblood over time, comprising: introducing blood into a chamber; andmeasuring conductivity of the blood using a pair of electrodes.
 13. Themethod according to claim 12, wherein the pair of electrodes is placedin a bottom surface of the chamber.
 14. The method according to claim12, wherein the change in conductivity is found based on a differencebetween conductivities measured at two points of time.
 15. The methodaccording to claim 14, wherein the two points of time are selected froma time section after the conductivity starts to decrease.
 16. The methodaccording to claim 15, wherein the erythrocyte sedimentation rate ismeasured through comparison of the change in conductivity with anerythrocyte sedimentation rate measured by the Westergren method. 17.The method according to claim 16, wherein a relationship between thechange in conductivity and the erythrocyte sedimentation rate measuredby the Westergren method is represented by the following equation:Δσ=λW ^(γ) where Δσ denotes a difference (unit: S/m) betweenconductivities of the blood measured at predetermined points of time, Wdenotes an erythrocyte sedimentation rate (unit: mm/h) measured by theWestergren method, and λ and γ denote fitting parameters, wherein thefitting parameters are calculated by regression analysis.
 18. The methodaccording to claim 16, wherein a relationship between the change inconductivity and the erythrocyte sedimentation rate measured by theWestergren method is represented by the following equation:Δσ=λ log(1+W) where Δσ denotes a difference (unit: S/m) betweenconductivities of the blood measured at predetermined points of time, Wdenotes an erythrocyte sedimentation rate (unit: mm/h) measured by theWestergren method, and λ denotes fitting parameters, wherein the fittingparameters are calculated by regression analysis.
 19. The methodaccording to claim 16, wherein a relationship between the change inconductivity and the erythrocyte sedimentation rate measured by theWestergren method is represented by the following equation:${\Delta \; \sigma} = {\lambda \frac{W}{W + \gamma}}$ where Δσdenotes a difference (unit: S/m) between conductivities of the bloodmeasured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, and λand γ denote fitting parameters, wherein the fitting parameters arecalculated by regression analysis.
 20. The method according to claim 16,wherein a relationship between the change in conductivity and theerythrocyte sedimentation rate measured by the Westergren method isrepresented by the following equation:${\Delta \; \sigma} = {\lambda \left\lbrack {\left( \frac{1}{\gamma} \right)^{2} - \left( \frac{1}{W + \gamma} \right)^{2}} \right\rbrack}$where Δσ denotes a difference (unit: S/m) between conductivities of theblood measured at predetermined points of time, W denotes an erythrocytesedimentation rate (unit: mm/h) measured by the Westergren method, and λand γ denote fitting parameters, wherein the fitting parameters arecalculated by regression analysis.